1. Field of the Invention
The present invention relates generally to tie back systems for lateral wellbores. More specifically, the invention relates to apparatus and methods for locating and setting a tie back system in a lateral wellbore. More specifically still, the present invention relates to an apparatus and methods for orienting a tie back assembly in a wellbore adjacent a casing window using a key and keyway and a no-go obstruction to rotationally and axially locate the liner with respect to the casing window.
2. Description of the Related Art
Lateral wellbores are routinely used to more effectively and efficiently access hydrocarbon-bearing formations. Typically, the lateral wellbores are formed from a window that is formed in the casing of a central or primary wellbore. The windows are either preformed at the surface of the well prior to installation of the casing or they are cut in situ using some type of milling process. With the window formed, the lateral wellbore is formed with a drill bit and drill string. Thereafter, liner is run into the lateral wellbore and xe2x80x9ctied backxe2x80x9d to the surface of the well permitting collection of hydrocarbons from the lateral wellbore.
Lateral tie back systems are well known. Various types are in use, including flush systems that allow a lateral liner to be mechanically tied back to the main casing at the window opening without the tie back means significantly extending into the primary wellbore. Other systems currently available place the liner in the main casing then xe2x80x9cchop offxe2x80x9d the portion of the liner that extends up into the main casing. Still other systems available utilize some form of liner hanger device placed in the main casing to connect the liner in the lateral wellbore to the primary wellbore. Some examples of lateral tie-back systems are detailed in U.S. Pat. Nos. 5,944,108 and 5,477,925 and those patents are incorporated herein by reference in their entirety.
There are problems with the currently available tie back systems. In those systems which utilize a liner hanger device placed in the main casing, the internal diameters of both the main casing and the liner are significantly restricted. Flush systems currently available are restricted to use in applications which use pre-milled windows containing control profiles precisely machined on surface prior to running in the wellbore which allow the tie back means at the upper end of the liner to be accurately landed in and connected to the window. Systems that sever a section of the liner extending into the primary wellbore require a milling process which is time consuming and expensive and always carries the risk of loss of the entire wellbore during the installation process. Another problem with conventional tie back systems is that survey devices must be used in the installation process in order to properly locate the assembly, which is expensive and time consuming. Existing liner hanger systems that use a permanent orientation device mounted on the tie back assembly to orient the liner window to the main casing take up space and significantly reduces the internal diameter of both the liner in the lateral wellbore as well as the main casing. Another problem with existing liner hanger systems using the bottom of the window for orientation is that they are set in compression, which limits the use of this equipment from moving platforms, such as floating rigs or drillships.
There is a need therefore, for an apparatus and method to complete a multilateral junction that will overcome the shortcomings of the prior art devices. There is a further need for an apparatus that can be installed in both existing and new wellbores and that does not restrict the internal diameter of the primary wellbore. There is a further need therefore, for an apparatus and method to complete a multilateral junction that allows selective access to both the lateral or to the primary wellbore.
There is a further need therefore, for a tie back system that more effectively facilitates the placement and hanging of a liner in a lateral wellbore. There is a further need for a tie back system that can be oriented using tension rather than compressive forces. There is yet a further need for a tie back system that can be rotationally located and axially located in a central wellbore using the central wellbore casing and/or a window therein as a guide. There is yet a further need for a tie back system that can be placed in a wellbore while minimizing the obstructions in the liner or the casing after installation.
There is yet a further need, for a tie back system that can be cemented in a wellbore and allows full casing access through the junction without restriction and which does not require any milling or the liner with the accompanying generation of metal cuttings which can cause numerous problem like the sticking of drilling and completion tools.
The present invention provides an apparatus and methods to complete a lateral wellbore that can be utilized for existing or new wells. The apparatus can be set in tension with positive confirmation on surface of correct orientation and position. Additionally, the apparatus does not restrict the internal diameter of the liner or the central wellbore and permits full access to both the lateral and the primary wellbore below the junction.
In one aspect, the invention includes a tie back assembly disposed at an upper end of a liner string. The tie back assembly includes a hanger, a packer and a tubular housing. The housing includes a liner window formed in a wall thereof to permit access to the lower primary wellbore. An inner tube is disposed within the housing and includes a key disposed on an outer surface for alignment with a window formed in a wall of the casing and a no-go obstruction which is constructed and arranged to contact a lower portion of the casing window to axially locate the tie back assembly in the primary wellbore.